The newborn is dependent upon fat for energy production. Fatty acid oxidation requires the cofactor carnitine. The preterm infant is born with limited carnitine reserves. During total parenteral nutrition (TPN) plasma and tissue carnitine concentrations decrease indicating that rates of carnitine biosynthesis are inadequate. The ability of the premature infant to oxidize fatty acids is related to the carnitine status. Several studies suggest an improvement of fatty acid oxidation after a fat challenge if TPN is supplemented with L-carnitine. Nitrogen balance may also be improved but this needs confirmation. It remains to be established whether routine L-carnitine supplementation is needed in neonatal TPN.